Numerous devices that are useful for the automated manufacture and assembly of products have been used successfully for many years. In each instance, these devices have been employed with a view towards increasing the efficiencies and accuracies of the procedures followed during the manufacture and assembly of a completed product. Indeed, the vast majority of consumer products are now produced with automated devices.
As the complexity of a manufactured product increases there may also be a commensurate increase in the complexity of the machines that are required to manufacture the product. This is particularly so where the component parts have small or irregular shapes, or where precision machining or assembly is important. For example, many products, including printed circuit boards, require that small components be accurately positioned and then inserted into other components. The process of positioning becomes increasingly difficult as smaller components are used, or where the components have irregular or varying shapes.
One type of device that has been successfully utilized as part of automated assembly systems is the linear voice coil actuator. Actuators of this type include an electromagnetic coil which interacts with a fixed-pole magnet. As is well known, when an electric current is applied to the electromagnetic coil, the coil generates its own magnetic field. If the electromagnetic coil is properly oriented relative to the fixed-pole magnet, this magnetic field that is generated by the electromagnetic coil will interact with the magnetic field produced by the fixed-pole magnet and cause the electromagnetic coil to move with respect to the fixed-pole magnet. Typically, in a voice coil actuator, a shaft is attached to the coil such that the shaft moves translationally with the moving coil. Further, a probe, gripper, or other tool may be attached to the shaft. In use, the tool which has been attached to the shaft is advanced by the actuator until the tool is positioned proximate an assembly component. The component is then manipulated by the tool and possibly moved by the actuator, as desired.
When using an actuator to move a product component, it is often desirable to move the component as quickly as possible in order to speed up the assembly process. In pursuing this objective, the shortcoming of present actuators is that they are not able to accelerate and move components as quickly as is desired. Further, not only is it desirable that the components be moved quickly, they must also be moved and positioned with extreme precision. Thus, speed can be crucial. Not surprisingly, these concerns are most pronounced when it is necessary to move relatively larger components that have relatively larger masses.
The basic problem confronted in the operation of a voice coil actuator involves quickly accelerating and decelerating the motion of the actuator and the component that is being moved. If proper control is not maintained, there can be an unacceptable overshoot of the desired position of the component. As indicated above, this problem is more severe with components having relatively larger masses, and when the actuator and component are moving at a relatively high velocity. A solution, however, is to provide an actuator which is capable of generating greater accelerating and decelerating forces. Greater forces, however, generally mean larger actuators. But, large actuators are not always practical, since space and weight limitations often require an actuator that is relatively small and relatively compact.
In light of the above, it is an object of the present invention to provide an actuator that can quickly accelerate components having relatively large masses. Another object of the present invention is to provide an actuator that can move components having relatively large masses at a relatively high velocity. Another object of the present invention is to provide an actuator that can quickly decelerate and accurately stop the motion of an actuator and a component. Still another object of the present invention is to provide an actuator that is compact. Yet another object of the present invention is to provide a high velocity, accurately stoppable, compact actuator, which is easy to manufacture, simple to use, and comparatively cost effective.